Method and apparatus for monitoring electrocardiogram (ECG) signals

Abstract

A method and apparatus for monitoring ECG signals are described characterized in that an ECG signal wave is detected, filtered to pass only a frequency band within a range of about 25-300 Hz, and stored in a first storage device; and each successive ECG signal wave is then detected, similarly filtered, and stored in a second storage device. Each of the successive signal waves, when stored in the second storage device, is cross-correlated with the signal wave stored in the first storage device, and a determination is made whether the maximum cross-correlation coefficient exceeds a predetermined value. Each of the successive signal waves having a maximum cross-correlation coefficient exceeding the predetermined value is averaged with the waves stored in the first storage device following which it is stored in the first storage device in place of the signal wave previously stored therein, and is also displayed.

What is claimed is: 
     
       1. A method of monitoring ECG signals, characterized in: detecting a first ECG signal wave, filtering same to pass only a frequency band within a range of about 25-300 Hz, and storing the filtered signal wave in a first storage device;   detecting each successive ECG signal wave, similarly filtering same to pass only a frequency band within the range of about 25-300 Hz, and storing the filtered signal wave in a second storage device;   cross-correlating each of said successive signal waves, when stored in said second storage device, with the signal wave stored in said first storage device, and determining whether the maximum cross-correlation coefficient exceeds a predetermined value;   averaging, with said signal waves stored in said first storage device, each of said successive signal waves having a maximum cross-correlation coefficient exceeding said predetermined value, and storing the averaged signal wave in said first storage device in place of the signal wave previously stored therein;   and displaying the average signal wave stored in said first storage device.   
     
     
       2. The method according to claim 1, wherein only the PQRS segment of the first ECG signal wave, and each successive ECG signal wave, is detected, filtered and cross-correlated. 
     
     
       3. The method according to claim 1, wherein said predetermined maximum cross-correlation coefficient is at least 80%. 
     
     
       4. The method according to claim 1, wherein said first ECG signal wave, and each successive ECG signal wave, is digitized and Fast-Fourier Transformed before being filtered, and inverse Fast-Fourier Transformed after being filtered and before being stored in its respective storage device. 
     
     
       5. The method according to claim 1, wherein the detected ECG signal waves are filtered to pass a frequency band within the range of about 40-200 Hz to detect particularly the HIS-bundle. 
     
     
       6. The method according to claim 1, wherein the detected ECG signal waves are filtered to pass a frequency band within the range of about 80-200 Hz, to detect particularly small infarcts. 
     
     
       7. The method according to claim 1, wherein the detected ECG signal waves are filtered to pass a frequency band within the range of about 25-100 Hz, to detect particularly late-potential activity. 
     
     
       8. Apparatus for monitoring ECG signals, characterized in that it includes: detecting means for detecting successive ECG signal waves;   filter means for filtering the detected ECG signal waves to pass a frequency band within a range of about 25-300 Hz;   first and second storage devices;   means for initially storing the first detected and filtered ECG signal wave in said first storage device, and for storing each successive filtered ECG signal wave in said second storage device;   cross-correlation means for cross-correlating each signal wave stored in said second storage device with that stored in said first storage device, and for including means determlning whether the maximum cross-correlation coefficient exceeds a predetermined value;   averaging means for averaging, with the signal wave stored in said first storage device, each of said successive signal waves having a maximum cross-correlation coefficient exceeding said predetermined value, and for storing the averaged signal wave in the first storage device in place of the signal wave previously stored therein;   and display means for displaying the averaged signal wave stored in said first storage device.   
     
     
       9. Apparatus according to claim 8, further including a digitizer for digitizing each of said ECG signal waves before it is filtered by the filtering means. 
     
     
       10. Apparatus according to claim 8, further including Fast-Fourier Transform means for transforming each ECG signal wave from the time domain into the frequency domain before being filtered;   and inverse Fast-Fourier Transform means for transforming the filtered ECG signal wave from the frequency domain back to the time domain after being filtered and before being stored in its respective storage device.   
     
     
       11. Apparatus according to claim 8, wherein said detecting means detects only the PQRS segment of each ECG signal wave. 
     
     
       12. Apparatus according to claim 8, wherein said averaging means averages, with the signal wave stored in said first storage device, each of said successive signal waves having a maximum cross-correlation coefficient exceeding 80%. 
     
     
       13. Apparatus according to claim 8, wherein said filter means passes only a frequency band within the range of about 40-200 Hz, to detect particularly the HIS-bundle. 
     
     
       14. Apparatus according to claim 8, wherein said filter means passes only a frequency band within the range of about 80-200 Hz, to detect particularly small infarcts. 
     
     
       15. Apparatus according to claim 8, wherein said filter means passes only a frequency band within the range of about 25-100 Hz, to detect particularly late-potential activity.